Fuel injection valve

ABSTRACT

A fuel injector, in particular, an injector for fuel injection systems of internal combustion engines, having an actuator, which cooperates with a valve needle, has a first valve closure member that is arranged on the valve needle, the valve closure member cooperating with a first valve seat surface on a valve body forming a first sealing seat. A second valve closure member cooperates with a second valve seat surface in the valve seat body forming a second sealing seat. The valve needle, or the first valve closure member, has a limit stop, against which, after a partial stroke of the valve needle, a counter limit stop of the second valve closure member strikes, lifting the second valve closure member from the second sealing seat in response to a further stroke of the valve needle.

FIELD OF THE INVENTION

The present invention relates to a fuel injector.

BACKGROUND INFORMATION

A fuel injector is already known which has a valve needle, that iscontrolled by an actuator. The actuator is composed, e.g., of anelectromagnetic coil or a piezo element. An exemplary fuel injector ofthe species, having an electromagnetic coil, is described in GermanPatent No. 35 40 660. The fuel injector has a valve housing, in which asolenoid coil is arranged on a coil support. A valve needle, having avalve closure member that is configured on the former as one piece,cooperates with a valve seat surface forming a sealing seat. At its endfacing the solenoid coil, the valve needle is fixedly connected to anarmature and is acted upon by a resetting spring against the sealingseat. If a current flows through the solenoid coil, the armature ispulled against the force of the resetting spring and lifts the valveneedle off from its sealing seat. The fuel can then exit through aspray-discharge bore hole which adjoins the valve seat.

A disadvantage in this known fuel injector is the fact that the angle atwhich the injection takes place is fixed, and the quantity of fuel canonly be regulated to a very limited degree. It is difficult orimpossible to make adjustments with respect to various operating states,such as are necessary in particular in the case of lean- mixtureconcepts and stratified-charge methods in combination with directinjection into the combustion chamber. For this purpose, it is necessaryto attain varying operating states using injection angles that vary intheir direction.

German Published Patent Application No. 32 28 079 describes a fuelinjector is known which has two valve needles. For converting fuel undermedium pressure to fuel under high pressure, the fuel injector has adifferential piston. Both valve needles are acted upon by one spring, ineach case, against one sealing seat. If the one valve needle is liftedfrom its sealing seat by the amount of a certain prestroke, then itstrikes against a limit stop of the other valve needle and, in thefurther stroke, it takes this valve needle with it. The two sealingseats of the two valve needles close different spray-discharge openings,which can be oriented at different angles. However, it is not possibleto achieve a substantial and individual adjustment with respect toperformance characteristics of an internal combustion engine, such as inthe case of a fuel injector that is controlled by an actuator. Inaddition, the design has many parts, and the interposition of adifferential piston results in a certain sluggishness of the fuelinjector with respect to its response performance.

German Published Patent Application No. 30 48 304 describes a fuelinjector for internal combustion engines, having a valve needle and anauxiliary needle in a bore hole of the valve needle. The valve needle,at its segment on the combustion-chamber side configured as a valveclosure member, cooperates with a valve seat surface to form a sealingseat, which separates spray-discharge bore holes from a fuel supply. Theauxiliary needle, guided in the valve needle, also has a valve closuremember, which cooperates with a second valve seat surface of the fuelinjector. As a result of a spring placed in the valve needle, theauxiliary needle is pulled against the valve needle, in which directionit also forms a sealing seat along with a valve seat surface in thevalve needle. If the hydraulically actuated fuel injector begins to openas a result of an increase in the pressure in the fuel supply line, thenthe auxiliary needle is pressed from its sealing seat in the valveneedle against the sealing seat in the valve body and closes a group ofspray-discharge bore holes, while a further group of spray-dischargebore holes is opened. If the pressure continues to increase, then thevalve needle is lifted from its sealing seat, and, after a certainstroke, it takes the auxiliary needle with it, the auxiliary needlestriking against the limit stop of the valve needle. All spray-dischargebore holes are then released. It is disadvantageous that the driving ofthe valve needle stroke is only carried out using the pressure of thefuel, and an adjustment with respect to the performance characteristicsof an internal combustion engine is therefore only possible to a limiteddegree.

German Published Patent Application No. 27 11 391 describes a fuelinjector having an operating piston for regulating the maximum stroke ofa valve needle. The valve needle is acted upon in the closing directionby a spring and cooperates with a valve seat surface to form a sealingseat. The valve needle is controlled purely hydraulically. Using theoperating piston, which is also hydraulically adjustable in its stroke,the stroke of the valve needle is limited, or completely prevented.Driving this operating piston is accomplished using its own supply line.In accordance with the stroke of the operating piston, the through-flowquantity of fuel can be limited. It is disadvantageous in the fuelinjector that the design is multi-part and cumbersome, and therefore isexpensive to manufacture.

SUMMARY OF THE INVENTION

In contrast, the fuel injector according to the present invention hasthe advantage of making possible in the combustion chamber of aninternal combustion engine a distribution of the fuel that is adjustedto the requirements of the performance characteristics and, inparticular, of a lean-mixture concept.

In particular, the angle at which the fuel is distributed in the jetimage of the fuel injector can be modified as a function of the valvestroke. This is assured in the fuel injector according to the presentinvention by the second valve closure member and by having the valveneedles driven by a common actuator. The fuel injector can be opened intwo stages, the sealing seats being opened one after the other.

Advantageously, as a result of the two sealing seats of the two valveneedles, two different hole circles, made up of spray-discharge boreholes, can be actuated.

In particular, the spray-discharge bore holes of the different holecircles can have different spray-discharge angles and can be offset withrespect to each other. Advantageously, when the injection quantities andthe loads of the internal combustion engine are slight, it is initiallypossible to open only a first hole circle. The latter has, e.g., anarrow spray-discharge angle of the spray-discharge bore holes, so thata fuel injection jet is formed having overall a narrow angle range. Inresponse to higher loads of the internal combustion engine and to thecorresponding requirements in the stratified-charge operation of aninternal combustion engine that is operated using a lean-mixtureconcept, the spray-discharge bore holes of the second hole circle areopened. The bore holes can be arranged at a greater spray-dischargeangle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a section of a fuel injector of the species, having avalve needle that is controlled using an actuator.

FIG. 2 depicts a segment of a first exemplary embodiment of a fuelinjector according to the present invention in a cutaway view.

FIG. 3 depicts a segment of a second exemplary embodiment of a fuelinjector according to the present invention in a cutaway view.

FIG. 4 depicts a segment of a third exemplary embodiment of a fuelinjector according to the present invention in a cutaway view.

DETAILED DESCRIPTION

Before three exemplary embodiments of a fuel injector according to thepresent invention are described in greater detail on the basis of FIGS.2 through 4, an already known generic fuel injector will first bebriefly discussed on the basis of FIG. 1 with respect to its essentialcomponents in order to achieve better understanding of the presentinvention.

Fuel injector 1 is executed in the form of fuel injector for fuelinjection systems of mixture-compressing, spark-ignition internalcombustion engines. Fuel injector 1 is especially suited for the directinjection of fuel into an undepicted combustion chamber of an internalcombustion engine.

Fuel injector 1 is composed of a nozzle body 2, in which a valve needle3 is guided. Valve needle 3 is in an operative connection with a valveclosure member 4, which cooperates with a valve seat surface 6, arrangedon a valve seat body 5, forming a sealing seat. In the exemplaryembodiment, fuel injector 1 is a fuel injector 1 that opens to theinside, which is provided with a spray-discharge opening 7. Nozzle body2 is sealed by a gasket seal 8 against outer pole 9 of a solenoid coil10, which functions as an actuator. Solenoid coil 10 is encapsulated ina coil housing 11 and is wound on a coil support 12, which contacts oneinterior pole 13 of solenoid coil 10. Interior pole 13 and exterior pole9 are separated from each other by a gap 26 and are supported on aconnecting part 29. Solenoid coil 10 is excited via a line 19 by anelectrical current that is supplied over the electrical plug-in contact17. Plug-in contact 17 is surrounded by a plastic sleeve 18, which canbe injection-molded on interior pole 13.

Valve needle 3 is guided in a valve needle guide 14, which is executedin a disk shape. To adjust the stroke, there is a separated adjustingdisk 15. Located on the other side of adjusting disk 15 is an armature20. The latter is connected via a flange 21 to valve needle 3 in aforce-locking manner, the valve needle being joined to flange 21 by awelded seam 22. Supported on flange 21 is a resetting spring 23, whichin the present design of fuel injector 1 is biased by a sleeve 24.Running in valve needle guide 14, in armature 20, and on valve seatsupport 5, are fuel channels 30 a through 30 c, which convey the fuel tospray-discharge opening 7, the fuel being supplied via a central fuelsupply line 16 and being filtered through filter element 25. Fuelinjector 1 is sealed by a gasket seal 28 against a cylinder head, or afuel distributor, which is not further depicted.

In the resting state of fuel injector 1, armature 20 is acted upon byresetting spring 23 opposite to the stroke direction, so that valveclosure member 4 is held in the sealing position on valve seat 6. Inresponse to the excitation of solenoid coil 10, the latter generates amagnetic field, which moves armature 20 in opposition to the springforce of resetting spring 23 in the stroke direction, the stroke beingstipulated by a working gap 27, in the resting position, located betweeninterior pole 12 and armature 20. In the stroke direction, armature 20also takes with it flange 21, which is welded to valve needle 3. Valveclosure member 4, in an operative connection to valve needle 3, liftsoff from the valve seat surface, and fuel is ejected throughspray-discharge opening 7.

If the coil current is switched off, after a sufficient degradation ofthe magnetic field, armature 20 falls away from interior pole 13, due tothe pressure of resetting spring 23, as a result of which flange 21, inan operative connection to valve needle 3, moves in opposition to thestroke direction. Valve needle 3 in this way is moved in the samedirection, as a result of which valve closure member 4 is placed onvalve seat surface 6, and fuel injector 1 is closed.

The section depicted in the cutaway view in FIG. 2 of a first exemplaryembodiment according to the present invention shows a valve body 31,which is configured in one piece along with valve seat body 32 and whichhas, e.g., a truncated-cone valve seat surface 33. A valve needle 34 isformed in one piece along with a first valve closure member 35, whichcooperates with valve seat surface 33 to form a first exterior sealingseat 36. Guided in a bore hole 37 of valve needle 34 is a second valveclosure member 38, which is acted upon by a force exerted by a spring39, which is supported against a bore hole base 37 a of valve needle 34.Second valve closure member 38 cooperates with a second valve seatsurface 40, which is arranged in valve seat body 32, forming a secondinterior sealing seat 41. In the embodiment described here, first valveseat surface 33 and second valve seat surface 40 are favorably providedas one single continuous surface in valve seat body 32, as a result ofwhich they are advantageously shaped from the production-technical pointof view.

Second valve closure member 38 has a collar 42. Serving as a limit stopis a step 43 in bore hole 37, the step being executed here as a sleeve43 a that is inserted into bore hole 37. Between first sealing seat 36and second sealing seat 41 are arranged spray-discharge bore holes 44around the circumference, which form a first exterior hole circle 45.Further spray-discharge bore holes 44 are arranged so that they can besealed both by first sealing seat 36 as well as by second sealing seat41 opposite a fuel supply 45 a, here indicated by an arrow, and so thatthey constitute a second interior hole circle 46. In addition, acentrally oriented spray-discharge bore hole 47 is also present, which,in addition to both hole circles 45 and 46, emits a fuel jet in thedirection of a longitudinal axis 48 of fuel injector 1. Spray-dischargebore hole 47 can also belong to interior hole circle 46.

If valve needle 34 is lifted by the actuator from its first sealing seat36, then initially only first hole circle 45 having its spray-dischargebore holes 44 is released. Only when collar 42 of second valve closuremember 38 contacts limit stop 43 of valve needle 34 after a partialstroke h₁ is second valve closure member 38 also lifted from its sealingseat 41, and spray-discharge bore holes 44, 47 of second hole circle 46,or centrally oriented spray-discharge bore hole 47, is released. As aresult, it is possible to individually adjust the angle at which thefuel injection jet fans out, taking into account the requirements of astratified-charge concept, or of a lean-mixture concept. It is onlypossible to open valve needle 34 in a stroke that is smaller thanpartial stroke h₁. If spray-discharge bore holes 44 of first hole circle45 have a smaller angle with respect to longitudinal axis 48, then thefuel injection jet, which arises and is here not further depicted, onlyfans out at a small angle in the combustion chamber. On the other hand,if a broad fanning out of the fuel injection jet at a large angle isdesired, then, as a result of an overall stroke of valve needle 34 thatis greater than partial stroke h₁, second valve closure member 38 canalso be lifted off from its sealing seat 41, and both hole circles 45,46 are opened. Through additionally opened spray-discharge bore holes44, which can have a different angle, it is possible to achieve adifferent shape of the fuel injection jet.

FIG. 3 depicts a segment of a second fuel injector according to thepresent invention in a cutaway representation of the lower segment,which is facing the undepicted combustion chamber. A valve body 49 isconfigured in one piece along with a valve seat body 50. A valve needle51, which is configured in one piece along with a first valve closuremember 52, cooperates with a valve seat surface 53 to form a firstinterior sealing seat 54. A second valve closure member 55 cooperateswith a second valve seat surface 56 to form a second exterior sealingseat 57. Second valve closure member 55 is supported via a spring 58against an intermediate plate 59 of valve body 49.

Serving as a limit stop of valve needle 51 is a circumferential collar60 of valve needle 51. The counter limit stop of second valve closuremember 55 is a circular groove 61 in an interior bore hole 62 of secondvalve closure member 55, through which valve needle 51 passes. Fuelsupply 63, which is indicated here by an arrow, is accomplishedcircumferentially outside of valve needle 51 and of first valve closuremember 52, and radially within second valve closure member 55, e.g., ina gap or one or more grooves between these two valve closure members 52,55. A further fuel supply leading to exterior spray-discharge bore holes64, which are arranged in valve seat body 50, is constituted radiallyoutside second valve closure member 55 of surrounding chamber 71.

Opposite fuel supply 63, a first interior hole circle 65, composed ofspray-discharge bore holes 64, is sealed by first sealing seat 54. Asecond exterior hole circle 66, made up of spray-discharge bore holes64, is sealed by second exterior sealing seat 57, opposite fuel supply63. Second valve closure member 55 on a third valve seat surface 68,which is arranged in valve seat body 50, has a third sealing seat 69,which seals second hole circle 66 opposite surrounding chamber 71, whichis filled with fuel. A further spray-discharge bore hole 64 is providedas a central spray-discharge bore hole 67 in valve seat body 50.

If valve needle 51 is lifted by the undepicted actuator, and if thestroke is smaller than partial stroke h₁, then valve needle 51 islifted, and first sealing seat 54 is released. Only spray-discharge boreholes 64 of first hole circle 65 and a centrally orientedspray-discharge bore hole 67 are now connected to fuel supply 63. If theactuator is activated to the extent that the stroke of valve needle 51is greater than partial stroke h₁, then second valve closure member 55is carried along by collar 60, which strikes against groove 61 in borehole 62. Second sealing seat 57 is now released opposite fuel supply 63,and third sealing seat 69 opposite surrounding chamber 71. The jet imageof the fuel injection jet can now be expanded if second hole circle 66has a larger spray-discharge angle with respect to a longitudinal axis70.

FIG. 4 depicts a fuel injector, in highly schematic form, in a cutawaycross-section corresponding to a third exemplary embodiment according tothe present invention. In a valve body 72, a valve needle 73 isarranged, which is joined to an armature 74 by a welded seam 76. Fromvalve needle 73, a second valve closure member 75 protrudes, similar tothe design according to FIG. 2. Valve needle 73 is acted upon by abiasing force via armature 74 by a spring 77. At spring 77, core 78 ofan electromagnetic actuator closes, whose coil is not depicted here.Arranged around valve needle 73, and fixedly connected thereto, is astop ring 79. Movably arranged in valve body 72 and supporting itselfagainst a step 82 in valve body 72 is a limit stop ring 80, which ispressed by a second spring 81 against this step 82. If armature 74 andvalve needle 73 are pulled by the armature, then, after a predeterminedstroke, stop ring 79 strikes against limit stop ring 80. To continue topull valve needle 73, the force of spring 81 must also be overcome.

As a result of this design, two different stroke ranges can be very welldistinguished so as to be easily controllable. In particular, it ispossible to distinguish two opening states of the fuel injector in aneasily controllable manner, if the stroke, after which stop ring 79comes into contact with limit stop ring 80, is selected so that itcorresponds to partial stroke h₁, of FIG. 2.

1. A fuel injector, comprising: a valve needle; a valve seat bodyincluding a first valve seat surface and a second valve seat surface; anactuator that cooperates with the valve needle; a first valve closuremember arranged on the valve needle and cooperating with the first valveseat surface on the valve seat body to form a first sealing seat; asecond valve closure member cooperating with the second valve seatsurface in the valve seat body to form a second sealing seat; and aspring supported against a spring receptacle, wherein: the valve seatbody includes a first circumferential hole circle element having aplurality of spray-discharge bore holes that are arranged in the valveseat body so that the first sealing seat seals the first circumferentialhole circle element with respect to a fuel supply, the second valveclosure member surrounds one of the valve needle and the first valveclosure member, the second valve closure member is guided by the firstvalve closure member and is biased against the second sealing seat bythe spring, a second circumferential hole circle element including aplurality of spray-discharge bore holes is arranged so that the secondsealing seat seals the second circumferential hole circle elementradially on an interior, and a third sealing seat, which is formed bythe second valve closure member having the valve seat body on a thirdvalve seat surface, seals the second circumferential hole circle elementradially to an outside with respect to a further fuel supply, and one ofthe valve needle and the first valve closure member includes a limitstop, at which, after a partial stroke of the valve needle, a counterlimit stop of the second valve closure member comes into contact andlifts the second valve closure member in a further stroke of the valveneedle from the second sealing seat.
 2. The fuel injector as recited inclaim 1, wherein: the fuel injector is for a fuel injection system of aninternal combustion engine.
 3. The fuel injector as recited in claim 1,wherein: a second circumferential hole circle element including aplurality of spray-discharge bore holes is arranged so that the firstsealing seat and the second sealing seat seal the second circumferentialhole circle element with respect to the fuel supply.
 4. The fuelinjector as recited in claim 3, wherein: one of the valve needle and thefirst valve closure member surrounds and guides the second valve closuremember.
 5. The fuel injector as recited in claim 3, wherein: thespray-discharge bore holes of the first circumferential hole circleelement have different spray-discharge angles with respect to thespray-discharge bore holes of the second circumferential hole circleelement.
 6. The fuel injector as recited in claim 1, wherein: the limitstop includes a circumferential collar, and the counter limit stopincludes a groove in a bore hole, in which one of the first valveclosure member and the valve needle passes through the second valveclosure member.
 7. The fuel injector as recited in claim 1, wherein: thefirst valve closure member and the second valve closure member arecoaxial with each other.
 8. The fuel injector as recited in claim 1,wherein: the valve seat body includes a central spray-discharge borehole.
 9. A fuel injector, comprising: a valve needle; a valve seat bodyincluding a first valve seat surface and a second valve seat surface; anactuator that cooperates with the valve needle; a first valve closuremember arranged on the valve needle and cooperating with the first valveseat surface on the valve seat body to form a first sealing seat; and asecond valve closure member cooperating with the second valve seatsurface in the valve seat body to form a second sealing seat, wherein:one of the valve needle and the first valve closure member includes alimit stop, at which, after a partial stroke of the valve needle, acounter limit stop of the second valve closure member comes into contactand lifts the second valve closure member in a further stroke of thevalve needle from the second sealing seat, the valve seat body includesa first circumferential hole circle element having a plurality ofspray-discharge bore holes that are arranged in the valve seat body sothat the first sealing seat seals the first circumferential hole circleelement with respect to a fuel supply, and the second valve closuremember surrounds one of the valve needle and the first valve closuremember.
 10. The fuel injector as recited in claim 9, wherein: the fuelinjector is for a fuel injection system of an internal combustionengine.
 11. The fuel injector as recited in claim 9, wherein the fuelsupply is arranged with respect to the first sealing seat, and whereinthe fuel supply is arranged circumferentially outside the valve needleand the first valve closure member and radially inside the second valveclosure member.
 12. The fuel injector as recited in claim 11, whereinthe fuel supply is formed by one of a gap and at least one groovebetween the first valve closure member and the second valve closuremember.
 13. The fuel injector as recited in claim 9, further comprising:a spring supported against a spring receptacle, wherein: the secondvalve closure member is guided by the first valve closure member and isbiased against the second sealing seat by the spring, a secondcircumferential hole circle element including a plurality ofspray-discharge bore holes is arranged so that the second sealing seatseals the second circumferential hole circle element radially on aninterior, and a third sealing seat, which is formed by the second valveclosure member having the valve seat body on a third valve seat surface,seals the second circumferential hole circle element radially to anoutside with respect to a further fuel supply.
 14. The fuel injector asrecited in claim 13, further comprising: a surrounding chamber, whereinthe further fuel supply to the outer spray-discharge bore holes radiallyoutside the second valve closure member is implemented from thesurrounding chamber.
 15. The fuel injector as recited in claim 13,wherein one of the limit stop of the valve needle and the first valveclosure member includes a circumferential collar, the counter limit stopof the second valve closure member is a groove in a bore hole, in whichone of the first valve closure member and the valve needle passesthrough the second valve closure member.
 16. The fuel injector asrecited in claim 13, wherein the spray-discharge bore holes of the firstcircumferential hole circle element have different spray-dischargeangles with respect to the spray-discharge bore holes of the secondcircumferential hole circle element.
 17. The fuel injector as recited inclaim 9, wherein the first valve closure member the second valve closuremember are coaxial with each other.
 18. The fuel injector as recited inclaim 9, wherein the valve seat body includes a central spray-dischargebore hole.